Swivel seat base



FIG. 1 is a top plan view thereof;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof; and

FIG. 7 is a perspective view of a swivel seat base showing my newdesign; and,

FIG. 8 and FIG. 9 show the applications of the present invention.

In the drawings, the broken lines depict environmental subject matteronly and form no part of the claimed design.

The ornamental design for a swivel seat base, as shown and described.